{"id":49456,"date":"2021-07-02T08:47:26","date_gmt":"2021-07-02T12:47:26","guid":{"rendered":"https:\/\/swling.com\/blog\/?p=49456"},"modified":"2021-07-02T08:47:26","modified_gmt":"2021-07-02T12:47:26","slug":"guest-post-recording-music-on-shortwave-part-2-weak-signal-recovery","status":"publish","type":"post","link":"https:\/\/swling.com\/blog\/2021\/07\/guest-post-recording-music-on-shortwave-part-2-weak-signal-recovery\/","title":{"rendered":"Guest Post: Recording Music on Shortwave Part 2 \u2013 Weak signal recovery"},"content":{"rendered":"

\"An<\/a><\/p>\n

Many thanks to\u00a0SWLing Post<\/em>\u00a0contributor,\u00a0TomL<\/a>, who shares the following guest post:<\/strong><\/p>\n

\n

Recording Music on Shortwave Part 2 \u2013 Weak signal recovery<\/h1>\n

by TomL<\/strong><\/p>\n

\"\"<\/a><\/p>\n

The QRM noise cloud surrounding my condominium motivated my first foray into noise reduction software to find a little relief (Please refer to Part 1 posted here<\/a>) using SDR recordings.\u00a0 I was able to use the freeware software Audacity<\/a> to reduce some of that type of noise to tolerable levels on strong broadcasts.\u00a0 But what about non-condo noise, like out in the field??<\/p>\n

NHK Japan<\/b><\/h2>\n

I took my trusty Loop On Ground antenna<\/a> to the usual county park Forest Preserve which is relatively low in RF noise.\u00a0 I did some usual recording on 25 meters and poked around for something being captured by SDR Console.\u00a0 On 11910 kHz is NHK broadcasting daily from Koga, Japan.\u00a0 It is hearable at this location but is always an S7 or weaker signal despite its 300 KW of power no doubt due to being beamed away from the Midwest USA.<\/p>\n

I recorded it using the SDR Console 10kHz bandwidth filter and created a separate noise recording from a nearby empty frequency.\u00a0 Here is the 2 minute portion of a Japanese music teacher. No noise reduction was applied:<\/p>\nhttps:\/\/swling.com\/blog\/wp-content\/uploads\/2021\/07\/NHK-Original.mp3<\/a><\/audio>\n

I opened the noise and broadcast recordings in Audacity to see what I could do.\u00a0 Part 1 of my previously mentioned post details how I apply the Noise file<\/a>.\u00a0 A big downside of using any kind of noise reduction software is that it is ridiculously easy to destroy the desirable characteristics of the original recording.\u00a0 Applying too much noise reduction, especially in the presence of constant, spiky lightning noises, will create both digital artifacts as well as very dull sounding results.\u00a0 So I used the Effect – Noise Reduction (NR) feature very carefully.<\/p>\n

In this example, I used the Effect \u2013 Amplify feature on the one minute noise file.\u00a0 I applied just +1dB of Amplify to the whole file.\u00a0 Then I highlighted a 10 second section I thought was representative of the general background noise and chose Edit \u2013 Copy.\u00a0 Then, I opened the broadcast file, Pasted the 10 seconds of noise to the END of the file and highlighted just the 10 seconds of noise. Then I chose Effect \u2013 Noise Reduction \u2013 Get Noise Profile button.\u00a0 Amplifying the noise file by +1db does not sound like much but it seems to help according to my tests.\u00a0 Anymore than this and the Noise Profile would not recognize the noise without destroying the music.<\/p>\n

I used the NR feature three times in succession using the following (NoiseReduction\/Sensitivity\/FrequencySmoothing) settings:\u00a0 Pass1 (3dB\/0.79\/1), Pass2 (2dB\/1.28\/1), Pass3 (1dB\/2.05\/0).\u00a0 Part of what I listened for was choosing the Residue circle and Preview button for any music or dialog that was being filtered out.\u00a0 If I heard something that came from the desired part of the recording in Residue, I knew that I hit the limit concerning the combination of Noise reduction and Sensitivity settings to engage.\u00a0 I used those Residue & Preview buttons over and over again with different settings to make sure I wasn’t getting rid of anything wanted.\u00a0 I also used the higher Noise reduction with lower Sensitivity to try to get rid of any momentary spiky type noise that is often associated with SWLing.<\/p>\nhttps:\/\/swling.com\/blog\/wp-content\/uploads\/2021\/07\/NHK-3Pass.mp3<\/a><\/audio>\n

I messed around with a lot of test outputs of differing dB and Sensitivities and a lot seemed to depend on the strength of the broadcast signal compared to the noise.\u00a0 If the broadcast was weak, I could push the dB and Sensitivities a little harder.\u00a0 I also noted that with strong signal broadcasts, I could NOT use more than 1 dB of Noise reduction beyond a Sensitivity of about 0.85 without causing damage to the musical fidelity.\u00a0 This was a pretty low level of nuanced manipulation.\u00a0 Because of these minor level Audacity software settings, it dawned on me that it is very helpful to already be using a low-noise antenna design.<\/p>\n

If the Sensitivity numbers look familiar, that is because I tried basing the series of Sensitivity on Fibonacci numbers 0.618 and 0.786.\u00a0 Don’t ask me why these type of numbers, they just ended up sounding better to me.\u00a0 I also needed a structured approach compared to just using random numbers!\u00a0 Probably any other similarly spaced Sensitivity numbers would work just fine, too.<\/p>\n

Now if you really want to go crazy with this, add Pseudo Stereo to your favorite version of this file (also detailed in Part 1) and playback the file using VLC Media Player<\/a>.\u00a0 That software has a couple of interesting features such as an Equalizer and a Stereo Widener.\u00a0 You may or may not like using these features but sometimes it helps with intelligibility of the voice and\/or music [VLC will also let you right-click a folder of music and choose to play all it finds there without having to import each MP3 file into a special \u201cLibrary\u201d of music tracks where they bombard you with advertisements].<\/p>\n

\"\"<\/a><\/p>\n

\"\"<\/a><\/p>\n

You can also turn on Windows Sonic for Headphones if you are using the Windows operating system.\u00a0 However, this can sometimes be too much audio manipulation for my tastes!<\/p>\n

\"\"<\/a><\/p>\n

Here is the resulting NHK noise-reduced file with 9ms of delay with High & Low Filters:<\/p>\nhttps:\/\/swling.com\/blog\/wp-content\/uploads\/2021\/07\/NHK-3PassPseudo.mp3<\/a><\/audio>\n

Radio Thailand<\/b><\/h2>\n

Five days later I was out in the field again.\u00a0 This time I found Radio Thailand on 11920 kHz finishing up a Thai broadcast.\u00a0 It was a weaker S5 signal than the NHK example, so it would be a good test.<\/p>\n

When I got home, I recorded the broadcast file at a Bandwidth filter of 8 kHz and using Slow AGC and the extra Noise file at 12kHz using Fast AGC.\u00a0 In a previous test I had noticed a very slight improvement in sound quality in the way noise seems to get out of the way quicker compared to Slow AGC (which is usually how I listen to shortwave broadcasters).\u00a0 I now try to remember to record the Noise file with Fast AGC.<\/p>\n

Here is the original without any noise reduction:<\/p>\nhttps:\/\/swling.com\/blog\/wp-content\/uploads\/2021\/07\/RThailand-Original.mp3<\/a><\/audio>\n

This time the Noise file using Amplify +1dB did not help and I used it as-is for the 10 second Noise Profile.\u00a0 I then tried multiple passes of NR at higher and higher Sensitivities and ended up with these settings the best: Pass1 (1dB\/0.79\/0), Pass2 (1dB\/1.27\/0), Pass3 (1dB\/2.05\/0), Pass4 (1dB\/3.33\/0).<\/p>\nhttps:\/\/swling.com\/blog\/wp-content\/uploads\/2021\/07\/RThailand-4Pass.mp3<\/a><\/audio>\n

As a comparison, I tried recording only with SDR Console’s noise reduction NR1 set to 3dB and got this.\u00a0 I hear more noise and less of the music coming through:<\/p>\nhttps:\/\/swling.com\/blog\/wp-content\/uploads\/2021\/07\/RThailand-NR1-3db.mp3<\/a><\/audio>\n

Now for more crazy Pseudo Stereo to finish up the Audacity 4Pass version (nice Interval Signal of Buddhist bells ringing and station ID at the very end):<\/p>\nhttps:\/\/swling.com\/blog\/wp-content\/uploads\/2021\/07\/RThailand-4PassPseudo.mp3<\/a><\/audio>\n

Summary<\/b><\/h1>\n

I do not understand why applying 3 or 4 separate 1dB Sensitivities of noise reduction is superior to just one Pass at 3dB Sensitivity (in Audacity) or the one 3dB noise reduction (in SDR Console).\u00a0 My guess is that doing 1 dB at different Sensitivities shaves off some spiky noise a little at a time, somehow allowing for more of the musical notes to poke through the noise cloud.\u00a0 Who knows but I can hear a difference in subtle musical notes and sharpness of voice and instruments.\u00a0 Probably the Fast AGC helps too.<\/p>\n

Music is a Universal Language that we can share even when we don’t understand a word they are saying. And there is more music on the air than I thought.\u00a0 Some of these recordings sound surprisingly pleasing after noise reduction. The fake stereo is pumped through a CCrane FM Transmitter to a few radios in the home, or I can use the Beyerdynamic DT990 Pro headphones.<\/p>\n

Enjoying the Music!<\/p>\n

TomL<\/p>\n","protected":false},"excerpt":{"rendered":"

Many thanks to\u00a0SWLing Post\u00a0contributor,\u00a0TomL, who shares the following guest post: Recording Music on Shortwave Part 2 \u2013 Weak signal recovery by TomL The QRM noise cloud surrounding my condominium motivated my first foray into noise reduction software to find a little relief (Please refer to Part 1 posted here) using SDR recordings.\u00a0 I was able […]<\/p>\n","protected":false},"author":15,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[3194,627,433,442,3,746,43,158,1113],"tags":[2785,9268,1163,737,5119],"class_list":["post-49456","post","type-post","status-publish","format-standard","hentry","category-guest-posts","category-how-to","category-mediumwave","category-music","category-news","category-recordings","category-shortwave-radio","category-software-defined-radio","category-tutorials","tag-field-recordings","tag-how-to-make-shortwave-recordings","tag-shortwave-music-recordings","tag-shortwave-radio-recordings","tag-toml"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_shortlink":"https:\/\/wp.me\/pn3uc-cRG","jetpack-related-posts":[{"id":56002,"url":"https:\/\/swling.com\/blog\/2023\/03\/guest-post-listening-to-lra-36\/","url_meta":{"origin":49456,"position":0},"title":"Guest Post: Listening to LRA 36","author":"Thomas","date":"March 5, 2023","format":false,"excerpt":"Many thanks to\u00a0SWLing Post\u00a0contributor,\u00a0TomL, who shares the following guest post: Listening to LRA 36 by TomL I finally had time to go outdoors to listen to LRA 36, Antarctica.\u00a0 People were gushing about how well it is being received.\u00a0 My location was a park across the street from the Forest\u2026","rel":"","context":"In "DX"","block_context":{"text":"DX","link":"https:\/\/swling.com\/blog\/category\/dx\/"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2023\/03\/SanGabriel-LRA-36.jpeg?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2023\/03\/SanGabriel-LRA-36.jpeg?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2023\/03\/SanGabriel-LRA-36.jpeg?resize=525%2C300&ssl=1 1.5x, https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2023\/03\/SanGabriel-LRA-36.jpeg?resize=700%2C400&ssl=1 2x, https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2023\/03\/SanGabriel-LRA-36.jpeg?resize=1050%2C600&ssl=1 3x"},"classes":[]},{"id":32854,"url":"https:\/\/swling.com\/blog\/2018\/06\/toms-field-portable-hf-antenna-snags-voks-summit-broadcast\/","url_meta":{"origin":49456,"position":1},"title":"Tom’s field portable HF antenna snags VOK’s summit broadcast","author":"Thomas","date":"June 20, 2018","format":false,"excerpt":"Many thanks to SWLing Post contributor, TomL, who shares a recording he made of the Voice of Korea on June 14, 2018. This English broadcast focuses on the Singapore summit and is, no doubt, historic in its content. [Note that we've posted other recordings on the Shortwave Radio Audio Archive.]\u2026","rel":"","context":"In "Antennas"","block_context":{"text":"Antennas","link":"https:\/\/swling.com\/blog\/category\/antennas\/"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2018\/06\/TomL-carroof-antenna-HF-field.jpg?resize=350%2C200&ssl=1","width":350,"height":200},"classes":[]},{"id":55580,"url":"https:\/\/swling.com\/blog\/2023\/02\/guest-post-old-fashioned-band-scan-after-the-solar-storms\/","url_meta":{"origin":49456,"position":2},"title":"Guest Post: Old Fashioned Band-Scan after the Solar Storms","author":"Thomas","date":"February 5, 2023","format":false,"excerpt":"Many thanks to SWLing Post contributor, TomL, who shares the following guest post: Old Fashioned Band-Scan after the Solar Storms by TomL This is just an old fashioned band scan to randomly see what I could hear after last week's solar perturbations when the Solar Flux Index went well over\u2026","rel":"","context":"In "Guest Posts"","block_context":{"text":"Guest Posts","link":"https:\/\/swling.com\/blog\/category\/guest-posts\/"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2023\/02\/NCC2pic.jpg?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2023\/02\/NCC2pic.jpg?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2023\/02\/NCC2pic.jpg?resize=525%2C300&ssl=1 1.5x, https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2023\/02\/NCC2pic.jpg?resize=700%2C400&ssl=1 2x"},"classes":[]},{"id":27718,"url":"https:\/\/swling.com\/blog\/2017\/08\/toms-am-broadcast-band-recordings-during-eclipse-totality\/","url_meta":{"origin":49456,"position":3},"title":"Tom’s AM broadcast band recordings during eclipse totality","author":"Thomas","date":"August 25, 2017","format":false,"excerpt":"Many thanks to SWLing Post contributor, TomL, for sharing the following guest post: August 21, 2017: Individual Recordings of MW During Totality by TomL I setup flimsy \u201cBackpack Shack\u201d loop antenna and preselector to my Sony ICF-2010 to listen to any propagation of MW signals as each transmitter experienced Totality.\u2026","rel":"","context":"In "AM"","block_context":{"text":"AM","link":"https:\/\/swling.com\/blog\/category\/am\/"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2017\/08\/Ferne-Clyffe-State-Park-Map.jpeg?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2017\/08\/Ferne-Clyffe-State-Park-Map.jpeg?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2017\/08\/Ferne-Clyffe-State-Park-Map.jpeg?resize=525%2C300&ssl=1 1.5x, https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2017\/08\/Ferne-Clyffe-State-Park-Map.jpeg?resize=700%2C400&ssl=1 2x"},"classes":[]},{"id":48848,"url":"https:\/\/swling.com\/blog\/2021\/05\/tomls-guide-to-making-and-optimizing-shortwave-radio-sdr-music-recordings\/","url_meta":{"origin":49456,"position":4},"title":"TomL’s guide to making and optimizing shortwave radio SDR music recordings","author":"Thomas","date":"May 9, 2021","format":false,"excerpt":"Many thanks to\u00a0SWLing Post\u00a0contributor,\u00a0TomL, who shares the following guest post: Recording Music on Shortwave by TomL I recently became curious about the seasonal music updates posted by Alan Roe.\u00a0 It is a nicely detailed list of musical offerings to be heard.\u00a0 Kudos to Alan who has spent the time and\u2026","rel":"","context":"In "Guest Posts"","block_context":{"text":"Guest 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